1. Field of the Invention
This invention relates to filament and yarn heating apparatus. In another aspect, this invention relates to a yarn heating device which can be readily serviced. In a further aspect, this invention relates to a process for servicing yarn heater devices. In another aspect, this invention relates to a yarn heater device with reduced likelihood of induction heater burnout upon failure of the temperature sensing element.
2. Description of the Prior Art
Yarn heating devices of the rotating roll type are well known in the textile industry. Such prior art yarn heaters comprise a roll providing a yarn engaging surface and a heater associated therewith to heat the roll. One such apparatus involves a rotating steel roll rotating about an induction heater. A common means employed to control the heat input to the induction heater contained in the rotating roll is to position a thermistor between the rotating roll and the induction heater. A problem arises upon failure of the thermistor in that repair of the defective heated rotating roll requires disassembly of the effected rotating roll in order to remove and replace the malfunctioning thermistor; thus repair must await shutdown of the entire yarn processing unit, typically containing tens to hundreds of heated rotating rolls.
Maintenance must therefore be postponed until a given yarn treating cycle has been completed, and then a very time-consuming procedure, i.e., disassembly and reassembly of the entire heated rotating roll is required, since access to the defective thermistor is provided only from the interior of the heated rotating roll.
U.S. Pat. No. 3,296,418 describes a yarn heater device which includes a heat sensing means embedded in the device heater. Complete disassembly of the device would be required to carry out any necessary maintenance on patentee's device, thus maintenance would necessarily be a time consuming process and would be delayed until the yarn processing unit was shut down.
U.S. Pat. No. 3,612,170 deals with a thermal treatment roll for textile yarns comprising a hollow rotor, a stator disposed inside the rotor and a connecting element composed at least partly of a solid, heat-conducting, lubricating material. The connecting element is further provided with a probe for temperature sensing embedded therein. Since access to the probe for repair or replacement requires disassembly of the roll, shut down of the entire yarn processing unit is necessary to allow servicing.
FIG. 1 illustrates a prior art driven roll assembly 1 with a mounting flange 3 and brackets 5 and 7 for attaching the driven roll assembly to a draw twister machine. Drive means for the driven roll assembly 1 is provided by gear 9 which attaches to the drive of the machine, not shown. Rotatable roll 11 is attached by bolt 13 on the front surface 14 of rotatable roll 11 to the rotatable shaft 10 which is driven by gear 9. Rotatable roll 11 is heated by induction coil 15. Mounted on base 8 of the driven roll assembly 1 is plate 17. Attached to the interior face of plate 17 is a continuous ring 19 surrounding rotating member 10 and induction coil 15. Ring 19 has an L-shaped cross section as shown in FIGS. 2 and 3. One leg of ring 19 is attached to the interior face of plate 17 by a plurality of screws 21. Sensor 25 is attached with epoxy cement 27 to the top surface 28 of the other leg of ring 19 which can be made for example of polytetrafluoroethylene. The sensor is held in position in the annulus defined by the outer surface of induction coil 15 and the inner surface of rotatable roll 11. Temperature sensor 25 is a thermistor sold by Fycon Engineering of Charlotte, N.C., sensor part #1947. Sensor 25 has connecting wires 29 and 39 which connect through respective solder dots 31 and 32 into connectors 33 (and 34 not shown) and two wires 35 and 37. Wires 35 and 37 are connected to the controls (not shown) of a draw twister. Input to induction coil 15 for heating rotatable roll 11 to the desired temperature for the yarn (not shown) wrapped on rotatable roll 11 is provided by the draw twister control. The connectors 33 and 34 and wires 35 and 37 are protected by tubular insulation 41 and 42 held in place by epoxy cement 43. A slot 45 (shown in FIG. 2) is provided in plate 17 for passage of the wires form sensor 25. A cable 46 also attached to the draw twister machine controls (not shown) provides power by connections not shown to induction coil 15 through slot 47 (shown in FIG. 1) in plate 17. Rotatable roll 11 has a back surface 23 (shown in FIGS. 1 and 3) adjacent to wires 29 and 39 which are connected to solder dots 31 and 32.
In prior art mounting of sensor 25 on continuous ring 19 as described in FIGS. 1, 2 and 3, the sensor may from time to time become inoperative and have to be changed. Frequently, a failure of the sensor can result in failure of the induction heater. The heater is subject to burn-out if the sensor becomes inoperative and thus signal the heater to continue heating in efforts to achieve a desired set temperature. In order to change the sensor mounted as taught by the prior art and as described in FIGS. 1, 2 and 3, the entire draw twister unit must be shut down and the driven roll disassembled since the only access to the defective thermistor is from the interior of the driven roll.
It is therefore an object of this invention to provide a yarn heater device. It is a further object of this invention to provide a yarn heater device which can be readily serviced to replace temperature sensing means disposed therein. It is also an object of this invention to provide a yarn heater device which can be serviced to replace temperature sensing means disposed therein without disassembling the yarn heater device. It is another object of this invention to provide a yarn heater device wherein access to the temperature sensing means is provided from the exterior of the rotatable roll. It is yet another object of this invention to provide a yarn heater device which is resistant to heater failure upon malfunction of the yarn heater device temperature sensing means.
It is another object of this invention to provide a process for replacing the yarn heater device temperature sensing means. It is a further object of this invention to provide a process for replacing the yarn heater device temperature sensing means without disassembling the yarn heater device. It is another object of this invention to provide an apparatus and process wherein the yarn heater device temperature sensing means can be replaced without disrupting the operation of the entire yarn processing unit.
It is another object of this invention to provide support means which maintain the yarn heater device temperature sensing means in close proximity to the inner surface of the rotatable roll.
It is yet another object of this invention to provide support means which maintain the yarn heater device temperature sensing means in position in the annulus defined by the inner surface of the rotatable roll and the outer surface of the heater. It is a further object of this invention to provide support means for a yarn heater device temperature sensing means which prevents heater burnout upon malfunction of the yarn heater device temperature sensing means.
It is another object of this invention to provide a process for conversion of a prior art yarn heater device wherein disassembling the yarn heater device is required in order to service the temperature sensing means to a yarn heater device wherein no disassembly is required in order to service the temperature sensing means. It is yet another object of this invention to provide a process for conversion of a prior art yarn heater device wherein access to the temperature sensing means is provided only from the interior of the rotatable roll to a yarn heater device with access to the temperature sensing means provided from the exterior of the rotatable roll.
These and other objects of my invention will become apparent from the disclosure and appended claims.